STRUCTURAL AND SPECTROSCOPIC CHARACTERIZATION OF A DICYANOOXOMOLYBDENUM(IV) COMPLEX WITH A TETRADENTATE SCHIFF-BASE LIGAND

The reaction of protonated tetracyanodioxomolybdate(IV) ion with 2-ace tylpyridine and ethane-1,2-diamine gave a new complex of formula [MoO( CN)(2)(L-L-L-L)]. H2P, where L-L-L-L = N,N'-bis[1-(pyridin-2-yl)ethyli dene]ethane-1 ,2-diamine. The structure of this salt was determined by , X-ray analysis. Principal dimensions (ranges or means; estimated sta ndard deviation +/-0.006 Angstrom) are Mo=O 1.689, Mo-C 2.157 and 2.16 8, Mo-N 2.273-2.329 Angstrom. The crystals are monoclinic, space group C2/c, a = 31.789(2), b = 8.194(1), c = 15.198(1) Angstrom, beta = 104 .08(1)degrees, Z = 8; R = 0.032 for 4249 observed [F/sigma(F) > 4] ref lections. The molybdenum is seven-co-ordinated with the L-L-L-L ligand and oxygen in one plane and cyanide ligands above and below this plan e. The structure contains water molecules which form a network of hydr ogen bonds with cyanide ligands. The IR and ESR spectra, as well as th e results of ion-exchange and electrophoresis experiments, are in agre ement with this structure. The visible spectra in various solvents are dominated by metal-to-ligand charge-transfer bands with absorption ma xima linearly dependent on the Reichardt E(T) parameter. The complex u ndergoes one step, two-electron, reversible-oxidation with E(1/2) = 0. 77 V.